1. Field of the Invention
The present invention relates to an irrigation system for a medical device such as a phacoemulsification handpiece.
2. Background Information
The lens of an eye can be removed in a procedure commonly referred to as phacoemulsification (“phaco”). In a phaco procedure an ultrasonically driven tip is inserted through a small incision in the cornea and used to emulsify the lens. The tip extends from a handpiece that is held by a surgeon. The tip is coupled to an irrigation system that supplies an irrigation fluid to the surgical site. The tip is also coupled to an aspiration system that aspirates the irrigation fluid and the emulsified lens. The irrigation fluid provides a medium to remove the emulsified lens. Additionally, the irrigation fluid provides a medium to transfer heat generated by the ultrasonically driven tip.
When performing a phaco procedure emulsified lens tissue may occlude the aspiration line. The occlusion may increase the downstream vacuum pressure of the aspiration line. If the occlusion becomes dislodged the cornea will be exposed to the increased vacuum pressure. This large instantaneous vacuum pressure may cause the cornea to collapse. There have been developed various devices and systems for preventing a cornea collapse due to an occlusion in the aspiration line. For example, U.S. Pat. No. 5,106,367 issued to Ureche, et al. discloses a vacuum surge suppressor that limits the transient flow during a vacuum surge by increasing the resistance of the aspiration line.
Most phaco systems address the issue of occlusion and control of intraocular pressure with devices, sensors etc. in the aspiration system. The aspiration system is downstream from the eye. The control of pressure and flowrate in the eye is therefore somewhat limited. Such a system is similar to controlling the flow of water through a stream with a dam located at the end of the stream. Any input from a downstream dam will have a delayed and possibly attenuated effect on the upstream conditions. It would be desirable to integrate control and safety features in the upstream irrigation systems.
U.S. Pat. Nos. 3,812,855 and 3,920,014 issued to Banko disclose an irrigation system that contains a plurality of solenoid actuated valves which control the flow of an irrigation fluid to a surgical site. Each valve may have an adjustable needle to vary the flowrate and corresponding pressure of the irrigation fluid. The Banko system provides no intelligence as to an occluded condition or any type of feedback loop that can be used to control the intraocular pressure. It would be desirable to provide an irrigation system that can control the intraocular pressure and provide various safety features for an ophthalmic surgical procedure.